Being drug addictive is not considered as disabled.  However, you may claim him as a dependent if you meet the requirements below:

• They aren't claimed as a dependent by someone else.
• They are a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They made less than $4,050 in 2017.
• You provided more than half of their financial support More info